Redstone all turns into item form randomly

So this bug is this. Just now i was playing in my survival world and was trying to make a small redstone piston door. It happened 3 times when i would walk in a cirtain block all the redstone i had would turn into item form. This is the repeaters, redstone, and redstone torches. I wasnt using comparaters. Also when i placed down a stone pressure plate the same thing happened, and if it didnt happen then, when i stepped on the pressure plate it happened. this is really annoying because in my redstone world this happened! Also i was just finished with a large redstone part for a puzzle map i was making. It had took me a long time and then BAM all my hard work was gone! Im afraid of going into my redstone world again and i really would like to do this on single player to.

so the step by step thing, as best as i can get it, is this.

put a redstone something together
2. walk around it on lots of different blocks
3. place a pressure plate down on top of a block with redstone under it.
4. that should trigger it

I have optifine and TMI installed but it never did this before 1.5 came out.